Instrument for drawing circular and curvilinear lines



May 17, 1949. G. A. HAEDERER INSTRUMENT FOR DRAWING CIRCULAR AND CURVILINEAR LINES Filed June 30 1944 2 SheetSfSheet 1 jzde/for' GusTAve A. Hneoaa'ea May 17, 1949. G. A. HAEDERER INSTRUMENT FOR DRAWING CIRCULAR AND CURVILINEAR'LINES 2 slhets-sheet 2 Filed June 30, 1944 E. Q OW n m. v0

m L. d@ n w w F W. Y n. d

Patented May 17, 1949 OFFICE INSTRUMENT FOR DRAWING CIRCULAR AND CURVILINEAR LINES Gustave A. laederer, Philadelphia, Pa. Application June 30, 1944, Serial No. 542,939

12 Claims. 1

This invention relates generally to drafting instruments and more particularly to a changeable curve adapted for use by draftsmen for drawing such regular or irregular curves as the occasion may require and for readily making available the data by means of which any such curve may be readily reproduced.

One of the principal objects of the invention is to provide in such an instrument a means whereby curves which are arcs of true circles, as well as irregular curves variable in extremely ne degree, may be obtained.

Another object of the invention is the provision in such an instrument of an inherently flexible portion pivotally connected with the main body portion of the instrument in spaced relation with respect thereto, in combination with a plurality of means operative to variably adjust the position and relation of said flexible portion with respect to said body portion to thereby vary, as desired, the curvature of the drawing edge of said flexible portion.

Further objects and advantages will be apparent from the following detailed description in which like reference characters refer to like parts the drawings, in which:

Figure 1 is a plan view of one face of the instrument constructed in accordance with and embodying the present invention and in which the guide rule or beam portion of the instrument is shown in its straight line position;

Figure 2 is a top plan view of the main body member portion of the instrument;

Figure 3 is a plan View of the opposite face of the instrument showing the beam-setting dial graduated in divisions which represent the radii of circles;

Figure 4 is a sectional view of the instrument taken on line 4-4 of Figure 1;

, Figure 5 is a sectional view of the instrument taken on line 5-5 of Figure 1;

Figure 6 is a sectional view or the instrument taken on line 6-6 of Figure 1;

Figure 7 is a fragmentary view, partially in section taken on the line 7 1 of Figure 4 showing the instrument set for one position of the beamsctting dial;

Figure 8 is a similar view showing the instrument set for another position of the beam-setting dial;

Figure 9 is a fragmentary view of the central portion of a modified form of construction of the instrument; and

Figure 10 is a vertical sectional View of the `said modified construction of the instrument.

Referring more particularly to Figure 1 of the drawings, it will be observed that the drawing instrument essentially comprises a main body portion I 0; a relatively flexible beam portion I I positioned alongside the body portion and spaced therefrom; a pair of curved arm portions I2--I2 fastened to and interposed between each of the corresponding opposite ends of the body I0 and supporting the beam I I and a plurality of flexing means interposed between the body I0 and the beam I I for liexing the latter into various curved positions, the said means comprising a centrally disposed rotary flexing means I3 and a pair of slidable iiexing members I4 and I5.

The main body portion 10 Referring to Figure 2, the main body portion Ill which may be formed of any suitable relatively non-flexible material is preferably in the form of an elongated ilat ruler-like member having parallel opposed faces with certain undercut areas therein and having one straight side, the latter being formed into the ruling or drawing bevel edge I6, provided, on each face thereof, with a suitably graduated scale E.

At the center of the body I0 are the circular under-cut areas I'I, in each face of the body, and also at the body center is the open end slot I8 formed in the body I0 and located centrally of the undercuts I'I, all for a purpose to be hereinafter described. It will be noted that the circles forming the outline of the circular undercuts I'I' are not located wholly within the plane of the body Il), but that a portion of the same, which is less than degrees, is cut off by the upper edge of the body. The center flexing means I3 is located within the slot I8 and the undercuts I1.

The edge of the body I0 opposite from the straight beveled edge I6, on both sides of the center, is formed to provide a pair of oppositely inclined slightly :curved edges I 9 and 20, the main body I9 being thus widest at the center and tapering, along the edges I9 and 20, to the narrower opposite end extremities thereof. Each face of the body, in the area of the edges I9 and 20, is undercut at 2l and 22, and is provided with suitably graduated scales marked A and B and designated in the drawings by the reference numerals 23 and 24. The side flexing means I4 and I5 are disposed for slidable movement along these undercut edges I9 and 2U, as Will presently appear.

Formed in the body I 0 adjacent each end thereof are the holes 23-23 and 242l, these being provided for the purpose of securing the corresponding ends of each pair of the curved arm portions I2-I2 to the body Ii). Each face of the body, in the area of the holes 23-23 and 2li-24 is undercut as at 24a. It will be noted that there are several parts which are located on or fastened to the main body I0, namely the center iiexing means I3, the side flexing means I-i and l5, and the arms I2-I2. It will also be noted that each face of the body I0 has been undercut at those specific places where the several designated parts are to be located in order that, when the said parts are operatively mounted in position upon the main body portion of the instrument, the opposite faces of the latter will present smooth flat surfaces; suchsasis desir-able in drawing instruments.

The beam portion 11 It will be noted that the beam II, extending alongside of and almost the 'vfulllenjgth-of' the body I0, may be formed of Celluloid, xylonite, amber, wood, metal or any plastic fcomposition having the requisite degree of flexibility for the functions to be described. appearsiin-Figure 1, this beam I I, which has parallel faces, isrv long, flat and narrow, being wider at the center and taperinggradually inwidth to each end thereof. nthefformfshown in Figure 1;.the lower or inner 'edge 'ofthe-*beam I Iis' of arcuate, i. e.l circular, "form, while fits"-outer`" longitudinal edge 26 'is straightwheri thefble'am .is L in its uneXed-coni dition. i The beam *I I,f which is somewhat thinnerV than the body IIJ, is iso disposed operatively with 'respect to the ,body i III that in Aall'` of itsA various f positions of cuwaturel it -liessubstantially inthe plane of its suppo'rtinglbodyrl'u' (seel'igure 4).

The beam i issupportedf. inxtheposition shown inFigurelL lengthwise of thebody` I 0, by means of ",the arms' `lI 2-I2 e`extending upwardly' from' the llbodyil and curvingptoward eachpoth'er. Each endl21of'LtheLbeamfIlI'.isfprovi'ded with a hole ,2 8A in which,islreceivfejdA ailbu'shinglZa which bears' upon' la ,t bearing' ,pin 29,' preferablyjdrilled and tapped at eachfend' to` receivethe screws '3U-'-3I1, which ,pass through -'countersunk x--holes 'in the 'ends of 'the' 'curvedgarms H4-I2, thuspivotally A.securing ...the ends `.."o`fl'the",beam Yto the `upper Y` lendsoftheicurved arms. Theibeam II is also t.provided .withl ,a` hole`13 Ilthrough the vvcenter there- .ofgeiteiidingjatmight angles Ltoithe plane thereof ,and with, a t'ransverselyv extendingl bore v32, this "bore extending throu'gh a' part of i the 'beam I I J from 'the' edge'j25A of the beaminwar'dly to the .hole 3|.

Asshown. inlFigure `A1,t he `outer edge 26 of the .beam I. I i. el, thegeldge .most remote. fromthe body lll;islstraightiwhereasthe"inner edge .25 ofthe "beam iis of .arcuate curvature ,coinciding with the ,.arcof'a circle. IIti's' Within the. scope 'of this invention. tc'rhave` the shapes lof the edges of the `beam changed withrelation' to each 'other 'with- Loutdep'arting [from the` spirit 'of '.the ;invention` .and without.jdetractingfromithe. accurate opera- 'tionf thefdraiiv'ingl instrument. Speci'i'ically,the e'dgeshapes may be' reversed' with the edge `26 fof jarcuate', i. e., circular' curvature, andthe edge `;.25"straight,[or"both.,e.dges"25 and 26 may be .arcuately-.curved .The theory .ofthe 'invention .supportingthefstatement'that the accurate op- ;eration of thedrawing instrument 4will not be effectedjbytheabove 'changesJinthe shape of'the edges of thebeam, .wiilqbe .setj'fortn after the instrument itself' has-LbeenL fully described.

@Thearms 12-12 The pair of armsI2-`='I2, whicheare secured to each opposite "end gof therbeam II, -are also -se-` cured to feach'fend-of the'body "I0" by means of the screws 33+33`` which Afreely* pass through a holeuinone ofthe Aarms I-2 andthreadedlyienvga-geaAA tapped hole in theother A'of thev arms I2. *Interposedbetween thebase'portions 34 ofy each pair of the arms I -2'-"I 2' is the-undercut end'vporytion 24a"of'thebody IIJ. 'I'Each of'the'lower holes {2d-'24 provided in' the undercutendiporton of ji-the'mainibodycmember In vis--i-lttedwith a spacer 1235thrcugh-Which-extends Jche i'securing screw` 4 33. Interposed between the spacer 35 and the hole 24 in which it is fitted is a bearing sleeve 35a about which the lower ends of the arms I;2-'I2 4araadaptedto pivot. P-Theiupper holes l -23-23 L4-a-relalso fitted-with`sspacers 36 through -Which the screws 33 pass. However, clearance vvis provided between each spacer 36 and its corirespondingrholetl, to thereby permit the arms IZ-QI'Ziand the beam II to pivot about the lower pin 35 withinthe limits afforded by the clearance nbetween'the'spacer 36 and its accommodating :hole;23.

l The central rotary flexing means 13 D Referring to Figures 1 and 4, the center flexing -means I-3r. includes. aninverted` U eshaped' member e31- slidably tted .Tinto vthexopen-,end slot I8 1in the'fbody- IIJ. -Provided inthe Vloase.;portion.of Ithe U -shaped member-,3T is* a :'holeS'Ia through 0 whichy 'freelyg-pa'sses; thezthreadedfashank- :38 'cran inverted If-shapedfmember; thevhorizontal'portion of which is in the formofzfa:shortltubular element v:3 8a. i The said threaded shank, xafter passing lthrough the hole in the :abase'A of- ;theeU shaped member 3'! ,azcontinues through! the vbore ,3 2 inthebea-mfI Isf-and isthreadedinto a1cylindrically shaped member 39 which isclosely: ttedinto lthe-holelfinthe:beam II. Affastening nut 40 @is .threadedon the-member 138 tand, when tight- ,30 tened;y holds "these parts .-in r place). as shown. Passing through `ithe.A shorty ytubular element ',38a forming the ahead ;of ,thef` member 38 .is-the .Y freely rotatable-pin -4 I f-uponthecoppositely pro- ,jecting vendsofwhichLare secured similar rollers m2-42. These -r-ollers FAZ-42 respectively ride inthe Aspirally shaped cammath slotsy 43-43 l1respectively formed in circular cam members .-M--li 1i; the l l-atter 4being P respectively fitted.A in the circular-undercut;portions I'Iformed in eachfop- 40.3 positea-faceof the. body rIIJ. .The ycarrr'members 44--44 move togethenfbeing-.secured to eachother V,by an,eccentricallyipositionedahub 'member 45, .which.is :provided-with avhexagonal shaped recess or socket .46- extendingl therethrough. .The pur- 45-posefcf the socket 46ris-.tolpermit-.the insertion of a hexagonally-shaped` keyrtherein'` (not shown) -by means .of which the cam l-membersy 44-44 may be readilyfturnedrtorfany desiredposition. Securedto the: outer-faces of; thev `cam members .M -Mare. the-.two graduatedfdial plates-Mantilla 'fby means :of which I'the required fpositional-iadjustment turning of the cam membersM--d may l be lvisuallyfdetermined :and zindicated. `The dial e1 is graduated, asfseenzfinlFigure l-,intozuniform ldivisions 4and' subdivisions'ltto .form a'fsuitable scale C. The dialMa'isgalsoagraduatedzto.provide lafscall-'eill asseerr inFiguregilcut its divisions and sub-divisions are.` non-uniform, the `graduations zbeing --suitably calibrated .to y'represent :the :radii toftcirclesafrom3.6` inchesrto 100 it., inthe model #of fthe. 'drawing instrument as shown. vIt'will Abe noted that the flexing means is relatively'xed -:in-place at thezlcenter :of :the tbody 110, except 4i for -z its own' rotary action, duei '-to Ithe spirally 165 grooved cam members 44-44 which are lockedin .1 the: .undercut circular portions I1, sincei thellatter if is .greaterfthanIBOfdegrees vanti-prevents anylateral displacement of these cam'imembers.

Inithe operationoftheexing means- I3,` when '.AFigure tlgfthe -cam paths 543-1431, acting on the rcllersfilZ--ifIZ,--causeftheimemberi38-tolbemoved andforc'e-the latter a-Way'from the'body i0. This causes i the lbeamtoiiex and to upivot"ab'out'the bearings 35e-35a and thus impart a curvilinear outline to the drawing edge 26 of the beam. Movement of the cams 44-44 in the opposite counterclockwise direction will positively draw the beam I I back toward the body I0, the movement of the beam II being positive in each direction due to the double cam faces of the spiral paths 43-43 acting on the rollers 42-42. An index l5 is provided on one face of the body I0 for cooperation with the scale on the dial 45, while an index 49 is provided on the opposite face of the body Ii! for cooperation with the scale on the dial 47.

The slidable flexing members 14 and 15 Referring particularly to Figures 1 and 5, the side flexing means I4 and I5, which are identical, are slidably disposed respectively between the inner edge 25 of the beam I I and each of the edges i9 and 25 of the main body IU. Each of these slidable flexing members I4 and I5 comprises a pair of dis-cs 50 and 5I)a (see Figure 5) held together by a central hub in the form of a tubular rivet 5l to provide each member with flanges 52 and 53 forming an annular channel or groove adapted to accommodate, on one side, the inner edge of the beam II and, on the other side, the proximate edge of the body I0. On the inner side oi each sliding member I4 and I5, the channel is attened, as at 54, to provide a substantial seat for the straight edge portion of the body I which is accommodated therein and along which the member is slidable, this attened portion 54 serving additionally to prevent rotation or rocking of the member about its central axis. Suitable shaped springs 55 are interposed between the flattened edge portions 54 of the channels and each edge I9 and 25 of the body member III to maintain the flexing members I4 and I5 in secure frictional engagement with the beam II and to prevent any accidental movement With respect thereto. An open index 55 is provided in the flange of each of the slidable flexing members lil and I to cooperate, respectively, with the scales 's3 and 24. The size and shape of the -exing members irl and I5 is such that, with the index 55 vset at zero, the beam II is not iiexed thereby. However, any movement of the members lil and i5 along their scales respectively 23 and de causes a force to be exerted tending to flex the beam il outward from the body IIl.

Operation En the use of the drawing instrument aboveA described for the purpose of drawing curves, other than arcs of circles, the beam II' is adjusted to the desired regular or irregular shaped curve by means of the center flexing means I3 and/or one or both of the slidable side flexing members ifi and l5. This is eiected by turning the dial All clockwise (see Figure 1), and by moving the side iiexing members I4 and I5 toward each other, from their zero positions, until the beam l I is curved to the desired position. One side iiexing member may be moved further than the other in forming an irregular shaped curve and the side ilexing members may be used, in

certain instances, without the center ilexing means. rlhe center exing means positively controls the movement of the beam I I in each direction toward and away from the body I0 and so may be employed to maintain the center of the beam l l iixed in position while the side vflexing members I4 and I5 are employed to outwardly flex the ends of the beam II, Thus, a

compound curve of almost any desired irregular shape may be obtained. It will be noted that the scales A and B in conjunction with their respective indices 56-56 on the slidable elements I4 and I5 and the scale C of the dial 4'! in conjunction with its xed index 48 may be used to accurately position the side iiexing members I4 and I5 and the center exing means I3 at any predetermined positions, or they may be used to accurately record their positions. The length of any given curve and/or the position of the same with respect to the drawing instrument, with the flexing means in given positions, may be determined by means of the scale E Von the bevel edge I6. Thus, by means of scale data recorded from the scales A, B, C and E of the drawing instrument, any curve may be accurately and quickly reproduced at any time and may be described for reproduction by one or more duplicate drawing instruments at any distance from the instrument making the original curve.

For the purpose of drawing arcs of true circles, the beam I I is flexed by the center flexing means I3 only, with the side flexing members I4 and I5 set and maintained at zero on the scales A and B. To do this, the instrument is reversed in position so that the dial 41a and consequently the scale D is uppermost. This dial is rotated counterclockwise (see Figure 3) to cause the beam II to be flexed in the manner already described. It will be noted that the iirst large division on the scale D is marked ft., indicating that when this division is opposite the index 49 that then the beam II is iiexed to a curve which is an arc of a circle having a radius of 100 ft. When the index is set at either of the two smaller divisions preceding the 100 ft. division, the beam II will be ilexed correspondingly to produce the true arcs of circles of 200 and 300 foot radii. At the position of the dial llla shown in Figure 3, and with the parts relatively arranged as shown in Figure 7, the beam II is aV straight line which is the arc of a circle having an innite radius. When the dial 4'1el has been turned 360 degrees, it will be noted that the beam II will then have been flexed to a curve which is an arc of a circle having a radius of 36 inches. Accordingly, for the model of the drawing instrument shown, the arcs will vary from those of circles of 36 inch radius to those of circles of 300 ft. It will be understood, of course, that diierent models may be provided suitably calibrated to produce arcs of circles of a radius range other than that shown in the drawings and described herein, without departing from the general principles and constructlonal details of the instrument of the present invention.

The outline of the beam I I has previously been described as having the straight edge 25 and the curved edge 25; it has also been set forth that the shapes of these two edges may be reversed or that the two edges may each be of curved shape without departing from the spirit of the invention or from the efficiency of the instrument in flexing the beam II into arcs of true circles. The force exing the beam II is exerted by the iiexing means I3 at the center of the beam il and this force acts to bend the beam which, at the same time, tends to pivot about the bearings 35. The structural resistance within the beam, to the bending action of the iiexing force imparted by the flexing means I3, due to the taper thereof from the center to the ends, decreases gradually from a maximum at the center of the beam to a minimum at the ends thereof and this c0rreien-soccer vsspondseenantalya-With thedecreaseiin 'the-@torque riaction-i-orr; the beamlfromzthe': center -tothecends of thetbeam; the torque :actionzatfithe-:rcenter :ci :,thezzbeam L' tending to."tiJ.rn` the same f1 about the 'bearing 35..':being11the maximum; and the'torque :action` atthe: ends ofi-the beam b'eingavmiirimum. ncc'ordingly; the curved tapered;construotioneof the :end :pivotedt beam I I providesf curves .which :arer arcs `of truer. circles. ,Thesesresult'sshave been mentfsucientlyntozpermitthe f'dra-ftsman--tolcon- 'venintlye grasp-ii'. the isamezfforzi operation thereof. ,mtzthefsame time; -theroppositeiknob'f t3: liesiwithrinithedepression:off thedi'al. face 61|. Land Yso insures ment. vNti'ieifr itisdesired to emplowtheidial' face -61.,':;the;operating keyfisfshifted'itofthef rightand :into .the dottedlineappositiom shownl -inyFigure 110, isiniwhish:caseithezoperating knob immediately asfsubstantated .byfexperimentsrby comparing; the v10 .isociatedewith:ftheirdial ifa'cefllzis `#flush therewith.

.' curves produceduby the drawing iinstrument-with therarcsziof crclesxkriown`y toibesaccurate. .'Infaalliof thesezinstanceslth'e.ourvesfproducednby thev draw :ing .instrument have matched perfectly: wthtarcs of the true1circ-les. 'Thescaleuin iact,=.has;:been

calibrated' byregisteringA the curve 'ofi th-eibeamt I `I -fwithiarcs of'trne :circles f-.Whose radii'rare-known Consequently, the :instrument-,sof Athemesent: finvention isfcapable oi employment. to1-measnre. and

ssiirrfalifother. respects;u,the= in'strument'zofrEigur es'f9 fiands ifis similan'zfbothin. constructionsv and in .op-

eration, to that previously described.

It willhe understood thaty thetdrawing instru l1.1-5 ment as "heriibefore described is susceptible of fvariousirotherl'changes and modifications which fmaybemadefrom time to timelwithout-'departing iroml: theitgeneral'lprinciples or real spirit of the Jpresentinv'ention, 1andnacc-,or'dingly,v Lit-isintended detenminezthe' radii'of arcs. oftruecircles. it-'rbegogtoi'claim the same Abr-oadly,asLwell as specifically,

ing merely necessaryvin order :torfacccmplish .this purposeitoV so :adjust the l dial E413@that'ithefiouter wedge of= therbeamw I I definesian .fare ,whichrisacoinl,fcident vvithu-tliatl of thezarcthe radiussof which: is

itoibe. determined. The -f graduation." onA thezdiallil .which iis then. iny registry-With the Aindex 49; provides lan.zaccurate'..indication :of thevra'dius -of the tarcbeing measured. Of. course, inwthisuse ofthe "instrument, .the sliding ielementsil 4; and.-rl-5Wil1-;be

:set iat 1;' their" zero vpoints f. .alongthe .fecales f Afiand :By one orthez' other. onboth of these'. elements bc -.ing, shifted'soutcof theinzero'. positions :only when i the: instrument yisfennol'oyedIto.-delineaterfcurves:of regular or Virregularzform which lare f'nottarcsfsof i true circles.

.figures-:9 and .losshowia modified construction off .the i instrument of i the i present invention, p :the purpose-1 of this modification lbeing tozprovideran arrangement which.dispenses :with the need of ffemployi-ngiy asep'arate .-or'independentfakeyiior.rei-- fecting rotationA of.either ofI the' center '.:dialss-IM andina -In general, this modiedzconstruction is; in all. respects 1 similar to. that `Vhereinbeforendeascribed. However, instead ofthe a-t fdialplates -fa's'indicated by theap'pendedolaims.

Whatifisfciaimed asnnew iand-fuseful is: lJAH'Idrating yfinstnurnerit comprisingta lmain cixidymiember,apivotally movable armssecured to .25 eeachffendzbfisaidibody member, af'fiexible beam se- .;.cured'fatiits ends-tofsaidmovable arms, theadja- 1cent'edgeszoffsaidbody member'fand .ofsaid lbeam Libeingspaced from'ieachother;andlslidable means disposed in sai'dlspace'andfinterengagingsaid1adv30 il jacented'ges forvvary-ing the Iposition -loflsaid beam swithiifesp'ectf tossaidilbo'dy.member. ythe said arms nbeing'siautomatlcallyf.shi'ftab1e 'relatively -to the .i-.bodyaazrxembentir-compensate'.forfvariations in the position :offvsaid lbea-m.

35 '12,. Aflrafting :instrument comprisingA arma-in body :membenxzallflexible b earn V'pivotally fsecured tatiitsienfdsi to2 said lbo'dy' member, rthe-adj acent eedg'essotrsaid;cbodytmember-and `.of said beam b'er.fingspacedfromfeach-othen' rotary means :at the 'fi-40 centeriofi: said'bodyiandr other means disposed in said space; onireach side'of' said: rotary means-*and vsiidable longitudinally with respect'to vsaid. body andtsa'id nbeam, :all 1 of L-sai'd Lmeans being opera- Ytive toivarythepositionzof' said? beam-'with respect -outer `acesoithe cam. .membersi 4 4MM f-asiinf-.the form cof` construction previously '..descri-.bed and :shoWnffinL-Figiures :lito: 8,..i-nelusive,: in theifmodir:fied construction ofiFiguresvQ and 4l0, thesexdial -lti'mi instrument-i011 use -in thelidelineation yand rfxneasurement :oficurvilinear/ lines ycomprisingv a relatively rigid imairrbodymember,faffiexible beam lipivotaily securedzat 'its opposite ends vto 1 corre- -.p1ates, .respectively designated by-thelefene toespondingienidseof-isaid mainubody member.' rotary :.numeralstD-andl are Ieachcentrallvdepressed, as-at -62,.-;to-provide.a circular4 seat. orf. depression .tor receiving-.therknoba3iof ianoperatingskey for rotating the' .-cam. members. Thisfkeyidncludeszia meansfinterposedtbetweensaid bod-y member' and said beam for positionally adjusting the latter into varying positions of curvature, said rotary .tmeans @bei-ngi'provided`` with I 1oppositelyA disposed ...shank-t4 which is non-rotatably, butf-slidably, :955 icaiibratedidials the surfaces of which are'respec- ,zittedwithin the bore- 65 of the centralfhubrmember 66 to which the cam members:AlleMnarei-secured. Identical operating knobs ISSL--itiiifavecseerati-ng key.. the -arrangement-beingilsuchuthatmhe key is adapted to' -befs-hiitedd laterallystoioneiside or the .otherrotthe main.bodyzotitheinstrumentiso thatsone or the othervofftfhe.operatingiknobs 83.-- y63- is seated withinf itsL corresponding depression -sure :that the outer-surf ace of theeknobi :G3i-wiperfectlyiflushiwith the surfaectoftthedial platenin i theIk depression: ofwhich Lthe foperatingtknobiis vseated.

`tively disposedsubstantiallyfflush With opposite Lffaces'ofsaidimain ybody' member, yand fixed indices .cozrisaictbodyrmemberforf'use in conjunction' with tneegradnationsofV said calibrated dials.

4in121am-instrument =as dened in claim 3 -whereinssaidoppositelyf'disposed "dials are each iig-fraduatedkior selective `use in= the delineation or :measurement fof .curvilinear lines vof different wharacter;

65 f- ."5'. Infian' instrument-ias v`defined in claim 3 zw:rer'eirrtsaidloppositelyf disposed dials are each :graduated forrsele'ctive use! inthe "delineation or :measurement of @curvilinear @lines of different character; zat least one Io'f theidials' being `calir Assuming, :for exam-ple; that itiisdesiredittofemv'2""1'0 nbratecl'ior use infthe :delineationior"measurement ployithe.instrument.with the d-ialirence-i4 Glimmer most; .the operating key. ist:shifteditottheffletteas i shown in Figure .110, in which positionithefoperating knob S31-for. rotatingetheidialawfisioutwandiy spacedzsfroxrf the uppermesti face of theiinstru-e zoficurvesevvhich are .'coi'nci'den'tiw-ith the .arcs of ecircles.

:6.51111- a-n/ instrument tas defined in l claim 3 l'whereinlmeansearefprovided.ifor efrectingl'rotary q'taiiistment VofssaidIrotaifymeans.

7. In an instrument as dened in claim 3 wherein said rotary means includes an operating means therefor in the form of an axially shiftable shaft non-rotatably keyed to said rotary means, said shaft being provided at its opposite ends with operating knobs and said oppositely disposed dials being provided with depressions therein for respectively accommodating said knobs in ush relation with respect to the outer surfaces of said main body member when said operating means is axially shifted to its full extent in one direction or the other.

8. In an instrument adapted to be disposed iiatwise for use in delineating or measuring lines and having a pair of rotatable scales respectively disposed upon opposite sides thereof with their outer surfaces substantially ush with the corresponding outer surfaces of said instrument, means for effecting selective rotation of said rotatable scales including an axially shiftable shaft non-rotatably keyed to said rotatable scales, said shaft being provided at its opposite ends with operating knobs and said oppositely disposed scales being provided with depressions therein for respectively accommodating said knobs in flushed relation with respect to said outer surfaces of the instrument when said operating means is axially shifted to its full extent in one direction or the other.

9. In an instrument having opposite flat surfaces selectively adapted to be disposed flatwise against a supporting surface for use in the delineation or measurement of lines, a relatively movable scale and index operatively provided in said instrument, and means for effecting relative movement between said scale and index including an operating key operatively associated with the movable element of said scale and index and shiftable laterally of the plane of said instrument, said operating key being provided at opposite ends thereof with operating knobs respectively adapted to be accommodated within depressions therefor formed in the opposite outer surfaces of the instrument, the arrangement being such that as said operating means is laterally shifted to its full extent in one direction or the other, the said operating knobs thereof are selectively disposed in flush relation with respect to their immediately associated outer surfaces of the instrument.

10. An instrument for use in the delineation and measurement of circular lines comprising a relatively rigid main body member, a flexible beam having its opposite ends movably secured to corresponding ends of said main body member, said flexible beam being provided with a free drawing edge and being characterized in that at least one edge of the beam throughout its full length extending freely between the movably secured ends thereof, when in unlexed state, is of a curvature capable of causing said free drawing edge to assume varying degrees of circular curvature when the beam is flexed upon the application of a force applied to the center thereof, and beam defiecting means interposed between said main body member and the midpoint of said beam operative to apply a deecting force to the beam for varying the curvature of the latter, said means being so disposed and operative relatively to the secured ends of the beam as to be capable of imparting to the free drawing edge thereof a curvature lcoincident with the arc of a circle, and additional means interposed between said main body member and said beam for varying the curvature of the latter in the regions thereof respectively extending between its pivoted ends and said first-mentioned means.

11. An instrument for use in the delineation and measurement of circular lines comprising a relatively rigid main body member, a flexible beam having its opposite ends movably secured to corresponding ends of said main body member, said flexible beam being provided with a free drawing edge and being characterized in that at least one edge of the beam throughout its full length extending freely between the movably secured ends thereof, when in unexed state, is of a curvature capable of causing said free drawing edge to assume Varying degrees of circular curvature when the beam is flexed upon the application of a force applied to the center thereof, and beam deecting means interposed between said main body member and the midpoint of said beam operative to apply a deflecting force to the beam for varying the curvature of the latter, said means being so disposed and operative relatively to the secured ends of the beam as to be capable of imparting to the free drawing edge thereof a curvature coincident with the arc of a circle, and additional means interposed between said main body member and said beam for varying the curvature of the latter in the regions thereof respectively extending between its pivoted ends and said first-mentioned means, said additional means being in the form of slidable elements, each of which bears an index for registry with calibrated position-indicating scales provided upon said body member.

12. A drafting instrument comprising a main body member, a flexible beam pivotally secured at its ends to said body member the adjacent edges of said body member and of said beam being spaced from each other, rotary means at the center of said body and other means disposed in said space on each side of said rotary means and slidable longitudinally with respect to said body and said beam, all of said means being operative to vary the position of said beam with respect to said body member, said beam being provided with a free drawing edge and being characterized in that at least one edge of the beam throughout its full length extending freely between the pivotally secured ends thereof, when in uniiexed state, is of a curvature capable of causing said free drawing edge to assume varying degrees of circular curvature when the beam is flexed upon the application of an edgewise pressure applied to the center thereof and along a line extending radially of its curved edge.

GUSTAVE A. I-IAEDERER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 199,917 Marshall Feb. 5, 1878 600,357 Clarkson Mar. 8, 1898 687,521 Elrod Nov. 26, 1901 772,622 Loring Oct. 18, 1904 1,091,246 Roehrig Mar. 24, 1914 1,650,269 Haederer Nov. 22, 1927 FOREIGN PATENTS Number Country Date 10,573 Germany Sept. 8, 1880 41,903 Austria Apr. 25, 1910 111,457 England Nov- 29, 1917 143,355 England May 27, 1920 

